X-ray inspection systems include an X-ray generator which typically comprises a heated cathode filament emitting an electron beam. The emitted electrons are accelerated towards a target. The electron beam strikes the target at a focal spot and some portion of the kinetic energy contained in the electron beam is converted into X-ray photons. At the focal spot, the photons are emitted in all directions from the target surface, whereby the intensity and energy of X-rays varies based on the angle with respect to the electron beam direction. The generated X-rays are allowed to leave a heavily shielded area only in a predefined direction.
Current x-ray inspection systems are very heavy, largely due to the massive amounts of shielding required to remove the X-rays produced in all directions from the target surface, except for those in the forward direction where the X-rays are used for radiography or other purposes. The problem is exacerbated by the use of electron targets made of materials having a high atomic number (high-Z). In contrast, low atomic number (low-Z) targets have a much more forward-peaked angular distribution, making it possible to eliminate a lot of lateral shielding. However, when large areas such as in mobile cargo radiography, need to be scanned, the x-rays from low-Z targets typically do not cover the usually vertical extent of the object very well because of this forward-peaked angular distribution.
In addition, mobile cargo inspection systems in particular, require an x-ray source optimized for weight and performance. Currently, weight is primarily determined by the required quantity of shielding materials.
Hence, there is requirement for a system and method to reduce shielding requirements, thereby reducing the overall weight of an x-ray source employed in an x-ray inspection system such as a mobile cargo inspection system.
What is also needed are methods of using magnetic and shaping techniques for low-Z targets that allow for the use of reduced shielding requirements and therefore, a system having an overall lower weight and improved coverage of the object using such low-Z targets.